Manual play electronic visual games are well known in the art. Representative disclosures of typical electronic visual games, and associated display circuitry, can be found in U.S. Pat. No. 3,631,457 to Hamada, et al.; U.S. Pat. No. 3,659,284 to Rusch; U.S. Pat. No. 3,659,285 to Baer, et al.; and U.S. Pat. No. 3,793,483 to Bushnell. The typical manual play electronic visual game is of the hockey, PING-PONG or tennis variety. The game is adapted to be played by a pair of players. Each player has a control unit, which he can use to control a cursor or paddle image, which is movable on a television or cathode ray screen. The cursor usually can be controlled in a single direction of movement only (for instance, up and down). The game circuitry also generates a puck or ball image, commonly a small square, which moves across the screen or "playing field". The circuitry which controls the ball calculates angles of incidence and reflection to duplicate as closely as possible, conditions under which an actual game might be played. The players are able to move their paddles along a single direction in order to deflect the moving square back into the other player's field of play. Normally, if the moving square and the cursor of a particular player do not intersect, the moving square moves behind the cursor; and a point is scored in favor of the opposite player. Thus, games similar to tennis, PING-PONG or volley ball can be played. Other more complicated games involve games somewhat similar to hockey, in that they involve making a shot in a specified goal area in order to accrue points. In these types of games, each of the players commonly controls a forward cursor and a number of rear cursors, which act as blocking cursors. However, the basic principles of the game remain the same.
Oftentimes, however, players who have become accustomed to various of the electronic visual games, find that it is becoming easier to play the particular game. Thus, the player's interest in the game begins to flag and the player may lose interest in the game completely and stop playing the game.
It is therefore desirable, if the electronic game has some facility for varying the velocity of the ball image both automatically and manually, to cause the ball image to move in an erratic fashion, thereby increasing the challenge of play.
What is needed, then, is a circuit which will generate control signals to cause the velocity of the ball, or puck image, to change at selected intervals automatically and also will control the velocity of the ball image by a signal introduced by a manual control.